There is a continued and growing need for better tools to evaluate the efficacy and effectiveness of modern medical care. This project will extend the development and application of the APACHE (Acute Physiology and Chronic Health Evaluation) severity of illness classification system to the analysis and study of modern ICU and hospital treatment of acutely ill patients. Successful completion of the project will not only improve the treatment of many severely ill patients, it could help reduce the amount of health care resources spent without benefit. To accomplish this, we will use a unique and richly detailed 6,500-patient, 15-hospital data base which includes demographics, diagnosis, information on severity of illness (APACHE), therapeutic effort, and hospital outcome. There will be four specific aims: a. Identification of profiles of low-risk ICU patients whose disease and severity of illness indicate they could be adequately and safely treated outside an ICU. b. Provide physicians with improved objective prognostic ability concerning outcome from severe multi-organ system failure that could be used in clinical decision making. c. Invstigate the variations and estimate the incremental value of pulmonary artery catheterization amoung severely ill patients. d. Link this data base with DRG definitions and analyze the interhospital stability of cost per case within DRG categories of ICU admissions. In addition to the above aims, this project will also provide data processing and analytic support for hospitals who request assistance in improving their use of ICUs or evaluating outcome from treatment. This will help make the transition from research development of APACHE to its use by professionals in improving their use of modern hospital services.